Domestic Refrigerating Appliance with an Evacuatable Storage Compartment

ABSTRACT

A domestic refrigerating appliance comprising a heat-insulated inner area, a refrigerating machine using a thermodynamic cycle for refrigerating the inner area, a vacuum pump and a first compartment which is separated from the inner area and which can be evacuated by means of the vacuum pump. The vacuum pump produces pressure inside the first compartment, said pressure being lower than the vapor pressure of water at the temperature of the compartment.

The present invention relates to a domestic refrigerating appliance comprising a heat-insulated inner area, a refrigerating machine using a thermodynamic cycle for refrigerating the inner area, a vacuum pump and a first compartment which is separated from the inner area and which can be evacuated by means of the vacuum pump. Such a refrigerating appliance is described, for example, in DE 198 58 254 A1.

The purpose of evacuating the compartment is to improve the keeping properties of the food stored therein. For this purpose, a uniformly low pressure must be maintained during the storage time. This pressure is usually of the order of magnitude of a few percent of atmospheric pressure. Its lower limit is determined by the design and quality of the vacuum pump, by the conduction capacity of conduits between the compartment and the pump, by the imperfect seal of the compartment and the conduits etc. Lower pressures can be achieved technically without any difficulties but require expenditure which increases the manufacturing costs of the appliance. Since the maximum attainable storage duration of chilled goods in a vacuum compartment only increases negligibly when the final pressure in the compartment is reduced, for example, below 1% of atmospheric pressure, there is generally no interest in achieving pressures of this order of magnitude in the vacuum compartment.

It is the object of the present invention to expand the possible uses of a refrigerating appliance of the type specified above.

This object is achieved by a refrigerating appliance having the features of claim 1. If the vacuum pump in the first compartment (10) produces a final pressure below the vapor pressure of water at the temperature of the compartment (10), water present in the compartment comes to the “boil”. The vaporization of the water at low pressure results in cooling of itself or cooling of chilled goods in thermal contact with the water so that a cooling temperature below that provided by the refrigerating machine to the inner area can be reached in the evacuatable compartment.

It is particularly preferable if the possibility is thereby provided to cool the compartment below the freezing point of water even if the temperature of the remaining inner area of the refrigerating appliance is higher. For this purpose, the vacuum pump must be capable of producing a pressure of 6 mbar or less in the compartment.

The refrigerating capacity depends on the volume flow extracted from the compartment. In order to achieve a refrigerating capacity which is useful in practice, the vacuum pump should develop a suction capacity of at least 0.5 l/s at the evacuation connection of the first compartment whilst in the first compartment, a pressure below the vapor pressure of water prevails at the temperature of the compartment.

Chilled goods other than water can be accommodated in a second evacuatable compartment which is in direct thermal contact with the first compartment.

This second compartment can preferably be evacuated independently of the first compartment. i.e. gas contained therein can be pumped away whilst the first compartment is separated from the pump or conversely. Thus, for example, after loading with chilled goods, it is possible to initially evacuate both compartments and after a certain time has elapsed or a certain pressure has been reached, the second compartment can be separated from the pump whether to have more suction capacity available for the first or to avoid drying out of the chilled goods in the second compartment by continuously pumping away the water vapor released by said chilled goods. It is also feasible to evacuate merely the second compartment and then connect the pump to the first compartment to start the refrigeration.

Since water vapor should not be released to such a great extent in the second compartment as in the first compartment, the suction capacity of the pump at an evacuation connection of the second compartment can be kept lower than at that of the first compartment.

In order to achieve direct thermal contact between the two compartments and to ensure that these are more closely thermally coupled to one another than to a remainder of the inner area, both compartments are preferably surrounded by a common wall.

The first compartment can preferably contain a hydrophilic porous material in order to provide a large surface on which water can evaporate.

In order to avoid water vapor pumped away by the vacuum pump re-condensing at an unsuitable location and/or to trap oil vapor of the vacuum pump, a condensate trap can be connected to the vacuum pump.

Conventionally, most refrigerating appliances comprise an evaporation tray which is supplied with water of condensation which becomes deposited on the evaporator of the refrigerating machine in the inner area of the refrigerating appliance. Such an evaporation tray can also be used for draining the condensation trap.

Further features and advantages of the invention are obtained from the following description of exemplary embodiments with reference to the appended figures. In the figures:

FIGS. 1 and 2 each show exemplary embodiments of the refrigerating appliance according to the invention in a schematic view.

FIG. 1 shows a schematic section through a domestic refrigerating appliance comprising a body 1 and a door 2 hinged to the body 1, which enclose a heat-insulated inner area 3. A cavity 4 is formed in a lower rear corner of the body 1 and accommodates the compressor 5 of a refrigerating machine of the refrigerator in a manner known per se. The compressor 5 supplies a condenser 6 attached to the rear wall of the body 1 with refrigerant at high pressure; from there the refrigerant reaches an evaporator 7 attached to the rear wall of the inner area 3 via a constriction and flows back from said evaporator to the compressor 5.

The cavity 4 also accommodates a vacuum pump 8 whose suction intake is connected to an evacuatable compartment 10 via a pipe 9. The compartment 10 is shown here approximately at half the height of the inner area 3 but can be placed at any other location; in particular, attachment near the bottom of the inner area should be considered in order to keep the pipe 9 short and thus enable effective evacuation of the compartment 10.

On its front side facing the door 2, the compartment 10 has a flap 11 which can be opened in the non-evacuated state of the compartment 10 in order to load or unload chilled goods. The flap 11 and the other walls of the compartment 10 each contain an insulation layer which thermally insulates the interior of the compartment 10 from the surrounding inner area 3.

A cooking pot 12 with a loose lid is shown as an example in the interior of the compartment 10. A water-impregnated cloth 13 is slung around the pot 12.

When the compartment 4 is evacuated, air escapes from the interior of the pot 12 since its lid is only resting loosely thereon. However, when the pressure in the compartment 10 approaches the final pressure in the range of a few millibar or fractions of millibar, hardly any gas escapes from the pot 12 so that a pressure substantially corresponding to the vapor pressure of the water at the temperature of the pot 12 is established in its interior if it contains water-containing chilled goods. This therefore avoids excessive drying out of the contents of the pot. If the pressure in the compartment falls to the vapor pressure of the water during evacuation of the compartment 10, the water with which the cloth 13 is impregnated begins to “boil”.

When the temperature of the compartment 10 is 0° C., the vapor pressure of the water is 6 mbar. One litre of water vapor at this pressure weighs 5 mg, and if the heat of evaporation of the water is 2250 J/g, 11 J is required to produce this. If the pump at the suction intake 14 of the compartment 10 develops a suction capacity of 1 l/s at the inlet of the pipe 9, this extracts 11 J of heat from the compartment contents per second, i.e. it develops a cooling capacity of 11 W. If losses of refrigerant via the walls of the compartment 10 are neglected, this means that if the melting heat of the water is 335 J/g, 50 minutes is required to make 100 g of water freeze from 0° C. Thus, for example, it is possible to produce ice cubes with the refrigerator according to the invention by placing an ice cube tray in the compartment 10 and evacuating this without the refrigerating machine needing to be capable of producing temperatures below 0° C. in the inner area 3. By setting the suction capacity of the pump to be higher at the connection 14, shortened cooling times proportional to the suction capacity can be achieved as required.

A condensate trap 16 is connected to a high-pressure connection of the vacuum pump 8 via a second pipe 15. A waste water line 17 leads from the condensate trap 16 to a condensation tray 18 which is mounted in a manner known per se on the compressor 5 in order to be heated by its waste heat and which collects the water of condensation which has collected on the evaporator 7 after being diverted from the inner area 3 through a hole in the body 1.

The exemplary embodiment in FIG. 2 differs from that in FIG. 1 in two aspects which can be achieved independently of one another.

The first aspect is that the refrigerator comprises a second evacuatable compartment 19 which is separated from the compartment 10 by a thin, heat-transmitting intermediate wall 20 and is surrounded jointly with this by an insulating outer wall 21 which separates the compartments 10, 19 from the remainder of the inner area 3.

The pipe 9 opens at the suction intake 14 into the lower compartment 10; a shut-off valve 22 in the intermediate wall 20 allows the two compartments 10, 19 to be separated from one another as desired or to be connected to one another for evacuation. In FIG. 2 each compartment 10, 18 is allocated its own flap 11; however, they could also be closed by a common flap. The compartment 10 can be loaded with chilled goods or it can be filled with water which merely serves to produce latent heat of evaporation during evacuation. The water can be brought in in the form of a water-filled flat tray or preferably in conjunction with a porous hydrophilic material such as cloth, fleece or foam which provides a large surface for the evaporation of water.

The second difference lies in the attachment of the evaporation tray 18 which is not mounted on the compressor 5 in FIG. 2 but in a base region 23 of the refrigerator below the heat-insulating bottom of the body 1. This base region 23 also contains a fan 24 and a condenser 25 which is placed between the fan 24 and evaporation tray 18 in such a manner that at the condenser 25 heated fan air passes over the water surface of the evaporation tray 18. 

1-12. (canceled)
 13. A domestic refrigerating appliance comprising: a heat-insulated inner area; a refrigerating machine using a thermodynamic cycle for refrigerating the inner area; a vacuum pump; a first evacuatable compartment which is separated from the inner area and which can be evacuated by means of the vacuum pump; and wherein the vacuum pump produces a final pressure within the first compartment below the vapor pressure of water at the temperature within the first compartment.
 14. The domestic refrigerating appliance according to claim 13, wherein the final pressure is below 6 mbar.
 15. The domestic refrigerating appliance according to claim 13, further comprising an evacuation connection between the first compartment and the vacuum pump, the vacuum pump developing a suction capacity of at least 0.5 l/s at a pressure prevailing in the first compartment below the vapor pressure of water at the temperature of the compartment.
 16. The domestic refrigerating appliance according to claim 13, further comprising a second evacuatable compartment which is in direct thermal contact with the first compartment.
 17. The domestic refrigerating appliance according to claim 16, wherein the first compartment can be evacuated independently of the second compartment.
 18. The domestic refrigerating appliance according to claim 17, wherein the suction capacity of the pump at an evacuation connection of the second compartment is lower than at that of the first compartment.
 19. The domestic refrigerating appliance according to claim 16, wherein the first and the second compartments are surrounded by a common wall.
 20. The domestic refrigerating appliance according to claim 13, wherein the first compartment contains a hydrophilic porous material.
 21. The domestic refrigerating appliance according to claim 13, further comprising a condensate trap is connected to the vacuum pump.
 22. The domestic refrigerating appliance according to claim 21, further comprising an evaporation tray into which the condensate trap drains.
 23. The domestic refrigerating appliance according to claim 22, wherein the evaporation tray is heated by heat loss of the refrigerating machine.
 24. The domestic refrigerating appliance according to claim 13, wherein the domestic refrigerating appliance includes a refrigerator. 